NY Next Generation Math NY-1.NBT.5

Math1st GradeUse place value understanding and properties of operations to add and subtract.

The Standard

Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used.

New York State Next Generation Mathematics Learning Standards

Teacher's field guide

What Students Need to Do: Students mentally find the number that is 10 more or 10 less than a given two-digit number. They explain that one ten is added or removed while the ones value stays the same, regrouping when needed.
What Mastery Looks Like: Given 46, a student states that 10 more is 56 and 10 less is 36 without counting by ones. The student explains the change as adding or removing one ten.
Common Misconceptions: Students may change the ones digit, count ten individual steps, or reverse more and less. They may state a memorized answer without connecting the change to the tens place.
How to Assess It: Give the number 54 and ask for 10 more and 10 less. Ask the student to explain the change with place-value language.

Lesson moves

Add or remove one ten-stick from a two-digit model, then state the new number without recounting the ones.
Ask students why the ones digit stays the same when 10 is added to 37.
Play ten-more-ten-less chain by passing a number card and naming both related numbers.
Update a supply count after receiving or using one package of 10 identical items.

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